Water dispersible granules (WDG's) are becoming increasingly important in the formulation of agricultural compositions because they are more safely handled and environmentally friendly than other commonly used formulations. For example, chemical spills of WDG's are easily cleaned, no toxic solvents are present in the WDG formulation, and it is possible to package WDG's in water soluble packaging, thus reducing user exposure.
The typical processes for making WDG's are pan granulation, spray drying, fluid bed granulation, and mixing agglomeration. The choice of which process to use depends on several factors, including the physical and chemical properties of the active ingredient(s), environmental and safety aspects, and volume and packaging requirements.
Pan granulation typically produces compositions having good dispersibility and can be used for low-melt, active ingredients. The disadvantage of pan granulation is that the granules are often dusty, and the size distribution of the granule is difficult to control. Spray drying typically produces compositions in high volume and with good dispersibility, however, the bulk density of the product is usually low and it is difficult to spray dry low-melt, active ingredients. Fluid bed granulation has basically the same advantages/disadvantages as spray drying, while mixing agglomeration has similar advantages/disadvantages as pan granulation.
Dinitroaniline herbicides, which are useful for the selective control of certain grasses and broadleaf weeds, have typically been formulated as emulsifiable concentrates, flowables, wettable powders or the like, which are diluted in a tank mix. These formulations, however, require handling, measuring and mixing prior to application to the soil.
Conventional dispersible granular compositions containing dinitroaniline herbicides have been difficult to prepare. Such herbicides, which are solid at room temperature but have melting points below 100.degree. C., have a tendency to cake, fuse or lump up when stored at or exposed to elevated temperatures, due to the excessive softening or partial melting of the herbicides. Moreover, they are often dusty and may cause staining.
The imidazolinone class of herbicides, such as imazaquin, imazethapyr, imazamethapyr and imazamethabenz-methyl, are highly desirable for the selective control of a wide variety of grass and broadleaf weeds in the presence of agricultural crops at exceptionally low rates of application. At present, imidazolinone herbicides are commercially available mainly in the form of liquid compositions. However, as environmental concerns increase, there is an ever-growing need for an effective granular composition containing an imidazolinone herbicide. The prior art's pan granulated compositions present the common drawbacks of dusting, variable particle size distribution, and lack of ease of water dispersibility.
Efforts to produce stable granular formulations comprising such dinitroaniline herbicides, alone, or in combination with imidazolinone herbicides, without the drawbacks discussed above, and capable of uniform distribution in a solvent-free, WDG formulation, however, continue.
It is therefore an object of this invention to provide a solvent-free, water dispersible granular composition with improved dispersion properties.
It is also an object of this invention to provide a water dispersible granular composition comprising a novel dispersion enhancing agent.
It is another object of this invention to produce a non-dusting, non-staining, water dispersible granular herbicidal composition having granules of substantially uniform size and density.
It is yet another object of this invention to provide storage stable water dispersible granular herbicidal compositions comprising one or more active ingredients.
It is further object of this invention to provide a novel method for producing water dispersible granular herbicidal compositions.
These and other objects of this invention will become more evident in the detailed description that follows.